1. Field of the Invention
The present invention relates to a method for fabricating a pixel structure and a pixel structure thereof. More particularly, the present invention relates to a method for fabricating a transflective pixel structure via three mask processes, and a pixel structure thereof.
2. Description of Related Art
Recently, with development of photoelectric technology and semiconductor manufacturing technology, flat panel displays (FPDs) are developed accordingly, in which since a liquid crystal display (LCD) has advantages of low voltage operation, no radiation, light weight, small size, etc., it is widely applied to a plurality of portable electronic devices such as laptop computers, mobile phones, personal digital assistants, etc.
However, for a general transmissive LCD applied to the aforementioned portable devices, if it is used outdoors or in an environment with strong external light source, images displayed on the LCD cannot be viewed clearly due to the excessive strong external light source. Therefore, a transflective LCD is generally applied to, which may not only utilize its own backlight source, but may also utilize an environmental light source to provide a reflective light source, so as to increase a luminance of the LCD. Therefore, the transflective LCD not only has the advantage of workable under a strong light, but may also effectively utilize the environmental light source as the backlight source for saving energy.
FIG. 1A to FIG. 1D are diagrams illustrating a fabrication flowchart of a transflective LCD. First, referring to FIG. 1A, a substrate 110 is provided, wherein the substrate 110 has an active device area A1 and a pixel area A2. Next, a gate 122, a gate insulating layer 124, a channel layer 126, a source 128a and a drain 128b are sequentially formed to form a thin-film transistor 120. Next, a patterned passivation layer 130 is formed to cover the thin-film transistor 120. According to FIG. 1A, the patterned passivation layer 130 has a contact opening P1, and the contact opening P1 is used for exposing the drain 128b of the thin-film transistor 120. Until now, the fabrication method is approximately the same to the fabrication method of a pixel structure of a transmissive LCD. It should be noted that the aforementioned structure generally requires four mask processes.
Next, referring to FIG. 1B, a patterned dielectric layer 140 is formed on the substrate 110 to cover the patterned passivation layer 130, and a portion of surface of the patterned dielectric layer forms a plurality of bumps 142. In detail, the steps of forming the patterned dielectric layer 140 are as follows. First, a dielectric material (not shown) is first deposited on the substrate 110, and the dielectric material (not shown) is a photosensitive material. Next, a photolithographic process is performed to the dielectric material (photosensitive material) via a mask process, so as to form the patterned dielectric layer 140. According to FIG. 1B, the patterned dielectric layer 140 has a contact opening P2 located above the drain 128b for exposing the drain 128b. 
Next, referring to FIG. 1C, a pixel electrode 150 is formed on the substrate 110. Generally, the fabrication method of the pixel electrode 150 includes following steps. First, a transparent conductive material (not shown) is formed to cover the patterned dielectric layer 140. Next, the transparent conductive material (not shown) is patterned via a mask process, so as to form the pixel electrode 150. It should be noted that the pixel electrode 150 is electrically connected to the drain 128b via the contact opening P2.
Next, referring to FIG. 1D, a patterned reflective layer 160 is formed on the pixel electrode 150. In detail, the steps of forming the patterned reflective layer 160 are as follows. First, a reflective layer material (not shown) is first deposited on the pixel electrode 150. Next, the reflective layer material (not shown) is patterned via a mask process, so as to form the patterned reflective layer 160. A region wherein the patterned reflective layer 160 is located is defined to be a reflective area R, and a region without the patterned reflective layer 160 on the pixel electrode 150 is defined to be a transmissive area T.
Compared to a general transmissive LCD requiring 5 mask processes, the transflective LCD requires 7 mask processes, so that fabrication time and cost are higher compared to that of the transmissive LCD. Therefore, reduction of number of the mask processes is a general trend in development of the transflective LCD.